1. Field of the Invention
This invention relates to the preparation of L-tryptophan by fermentation.
2. Description of the Prior Art
L-Tryptophan is useful as an essential amino acid, and an economical process for producing it on an industrial scale is in demand. Conventionally, L-tryptophan has been prepared by fermentation on a medium containing a precursor (e.g., indole, anthranilic acid or serine) (described in, for example, Japanese Patent Publication No. 27353/71) or by the "direct fermentation method" which does not use such precursor (described in, for example, Japanese Patent Publication No. 38795/76). The direct fermentation method that does not require a precious precursor is considered advantageous for production of the tryptophan on an industrial scale.